Gymnocypris przewalskii przewalskii (Kessler)and Nemachilus scleropterus Herzensteinare the only fish in te Qinghai Lake. Both of them are parasitized by two species ofacanthocephalans

Neoechinorhynchus qinghaiensis Liu et al.and Echinorhynchus gymnocyrii Liu etal.

which harbour in the intestine of the hosts. In the former host

E. gymnocyprii locates in theanterior section and N.qinghaiensis in the posterior section

but in the later host

the sites of twoacanthocephalan worms are not obviously different.Comparing concurrent infection with singlespecies infection

the site of N

qinghaiensis in the host G

przewalskii przewalskii moves backobviously and its intensity of infection in the host N.scleropterus decreased significantly

theniche overlaps of two parasites in two hosts decreased.The negative interspecific association oftwo acanthocephalan worms in two fishes are not significant.